Page 25 - Journal of Special Operations Medicine - Fall 2016

Figure 1 The four compartments of the leg, including P’s mnemonic) in the affected limb. Pain out of proportion
associated muscles, arteries, veins, and nerves. Used with to the seeming presentation should be the most notice-
permission. able and alerting finding in early ACS, because the other
symptoms often do not present until later and after irre-
versible nerve or muscle damage has occurred. Eliciting
1
pain with passive plantarflexion of the ankle can increase
pain in the anterior compartment and is a sensitive, but
nonspecific, bedside test for anterior compartment in-
volvement. Weakness occurs with dorsiflexion of the
ankle and flexion of the hallux, with diminished sensa-
tion occurring over the first interdigital cleft from deep
fibular nerve involvement. With lateral compartment in-
volvement, there is increased pain with passive supina-
tion of the ankle and sensation is lost over the dorsum of
the foot from superior fibular nerve involvement. Lateral
compartment syndrome typically occurs with anterior
compartment syndrome and rarely occurs in isolation. 2

Despite the importance of the clinical assessment, Bow-
yer references a study by Ulmer et al. that shows the
3
sensitivity of clinical findings for diagnosing ACS is
Reprinted from The Journal for Nurse Practitioners, Joanne Pechar, between 13% and 19%. Furthermore, the positive pre-
M. Melanie Lyons, “Acute Compartment Syndrome of the Lower dictive value of clinical findings was found to be 11%–
Leg: A Review,” Vol 12, pp. 265–270, April 2016, with permission 15%, and the specificity and negative predictive value
from Elsevier [based on a figure from Bowyer MW. Compartment syn-
drome. In: Gahtan V, Costanza MJ, eds. Essentials of vascular surgery was 97%–98%. Bowyer concluded that the probability
for the general surgeon. New York, NY: Springer; 2014:55–69]. 3,19 of ACS increases when more signs and symptoms are
a, artery; Ant., anterior; m, muscle; n, nerve; v, vein.
present, although it may be detrimental to the patient to
delay a suspected diagnosis if the purpose is to wait for
an increase in compartmental contents (usually blood or additional clinical findings to manifest. 3
edema) or a reduction in compartment volume that re-
sults in intracompartmental pressure. As edema within When the diagnosis is unclear, intercompartmental tis-
the restrictive fascial compartment increases, intralumi- sue pressures can be measured using various methods,
nal venous pressure increases to prevent vascular col- with arterial line transducer methods being the most ac-
lapse. This results in a decreased arteriovenous pressure curate; normal pressures in adults are typically around
gradient that leads to decreased capillary blood flow. 8mmHg. Pressure thresholds are controversial, but in-
4
The decreased capillary blood flow results in capillary tracompartmental pressures greater than 15mmHg in a
permeability and tissue ischemia. 1 symptomatic patient should prompt serious consider-
ation for surgical intervention. 3
One theory proposes that an absolute compartment
pressure exists and that increased intracompartmental Trauma is the most common cause of ACS, although
pressure causes capillaries to collapse. Another theory, compartment syndrome of the extremities has also been
that of critical closing pressure, hypothesizes that a min- reported with burns, surgical positioning (i.e., lithotomy
imal mean arterial pressure (MAP) must exist to prevent position), constricting casts and wrappings, nephrotic
the collapse of small arterioles. Studies have identi- syndrome, rhabdomyolysis, bleeding disorders, and in-
fied a MAP of approximately 30mmHg as the positive fections (most often involving Streptococcus species).
pressure intercept at zero blood flow. Since perfusion Delayed diagnosis and/or treatment can result in severe
pressure (PP) within a compartment is the difference complications, including renal failure secondary to mus-
between MAP and intramuscular pressure, PPs below cle necrosis, hyperkalemia and metabolic acidosis that
30mmHg have been shown to be unable to maintain tis- can lead to cardiac arrhythmia, infection of necrotic
2
sue viability. These mechanisms result in a continually muscle, loss of limb, permanent neurologic deficits, or
propagating cycle of worsening edema and diminishing death. Emergent fasciotomy as soon as possible after di-
perfusion that eventually leads to irreversible nerve and agnosis is the optimal treatment in ACS. 4
muscle tissue damage.
The diagnosis of compartment syndrome can be chal-
ACS can be diagnosed clinically by the presence of pain, lenging and may be misdiagnosed or overlooked com-
5
paresthesias, paralysis, pallor, and pulselessness (the 5 pletely. Bhattacharyya and Vrahas reviewed a number

Lower Extremity Compartment Syndrome in Airborne Operations 7